Dying alongside them were four British men who carried home-made bombs onto underground trains and buses and detonated them in the belief it would help their cause.
Around 700 people were injured. Some with just cuts and bruises, others using their own clothing as tourniquets after their limbs had been shattered, and hundreds more whose memories were scarred forever.
Many good people - police, doctors, nurses, firemen, bystanders, commuters - gave first aid and held the hands of the dying. The emergency services' radios did not work underground, and many were left to suffer, scared, alone and in the dark, without the help they should have had.
I was in central London on that day, but a long way from the explosions. I came out of a meeting and rang the office to say I was on my way back in, and was angry that my mobile kept dropping the call. It was only when I finally got through to the newsroom and was told "there's been a bomb, stay where you are" that I realised the telephone networks were under strain, and noticed the sound of sirens in the distance. I rang my mum to tell her I was fine and headed to the scene, and then the hospitals.
In the weeks that followed, four more men tried and failed to set off bombs, and innocent Jean Charles de Menezes was gunned down on the Tube by Security Services who wrongly thought he was a terrorist.
Reporters scrabbled to cover the story - to define the culprits, name the heroes, and find the words to explain. Politicians called for action although they could not say what and the police tried to find what had gone wrong. We now know that a private detective found - and maybe used - the mobile numbers of the victims and probably the bombers too, presumably with the intention of listening to their voicemails.
It has since been found that a series of failings by the Security Services had allowed those four killers to slip under the radar. It is difficult to know what any of us could have done over all the years of those men's lives to convince them that their hatred of their countrymen was unfounded; but obviously, somewhere, we failed too.
Six years on, the bombers have failed. Their attempt to bring terror produced astonishing heroism, created friendships among the survivors and their families, and did not stop survivors like Gill Hicks and Danny Biddle from walking down the aisle at their respective weddings, or Martine Wright hoping to enter the 2012 Paralympics, despite the fact their legs had been blown off. It made all those people determined to prove the world is still a bright and beautiful place.
If the men who detonated those bombs could see what they have wrought, they might have thought twice. Because they did not make any wars shorter, they did not stop any governments, and they did not prove their point.
All they proved is that the human spirit can triumph over pretty much anything.
